1. Field of the Invention
This invention relates to road surface marking tape materials for use on roadway pavements so as to provide a traffic regulating indicium thereon, such as traffic lane dividing lines, road lane edges defining lines and so on. More particularly, this invention relates to prefabricated tape material having wear-resisting properties, and principally (as far as the invention is concerned) anti-skid properties, provided by the fact that the material has a smooth highly wear resisting planar surface layer and a plurality of hard crystalline particles at least some of which include an upper portion extending outwardly from the upper face of said layer to impart good anti-skid properties to said face for vehicle traffic safety. The tape material concerned with the invention being also of the kind designed to be applied on and secured to the roadway pavement by means of lower "primer" layer best suitable for its anchorage with the pavement.
2. Description of the Prior Art
This art is a well known and worked one and several improvements had been made thereto. A number of Patents had been issued to the present applicant thereabout. Reference is herein made to the U.S. Pat. Nos. 3,872,843 and 3,935,365 for more complete acknowledgement of such prior art and of the problems concerned therewith.
One important problem descends from the most desirable anti-skid property of the material. The upper surface of the tape in service is firmly engaged by the vehicle wheel treads and therefore powerful thrusts occur to be applied tangentially on the said surface (the term "tangentially" refers to the wheel tread where contacting the said surface, that is directed in the plane defined by said surface), extremely powerful forces can be for example originated by a heavy and/or fastly traveling vehicle engaged in an emergency braking or by the centrifugal force during a curve. These thrusts tend to displace the tape in the direction of the force, that is cause the tape material to "slide" on the road pavement, detaching said tape from said pavement.
On the other hand such powerful thrusts are applied on the tape surface at a rather small surface area thereof, that is at the wheel tread-tape surface interface. Now, the tape material is secured to the (generally bitumen based) roadway pavement by means of an essentially plastic composition, even if the primer layer comprises completely hardened bituminous components. The resistance to said tendency of horizontally displacing the tape, under said thrusts, can provided at the tape material-road pavement interface (more properly, interlayer) at a very greater interfacial area.
In the practical service of said road marking tapes, as known to those skilled in the art, a tangentially applied powerful thrust can cause and frequently causes a localized damage to the tape material, which locally flakes off and wrinkles up, and sometimes is torn apart.
Complemental problems concern the desirable provision of tape material of small overall thickness (both for economy reasons and for limiting its overall height or protrusion from the actual road pavement surface) and the difficult and hard and fatiguing operation of removing, when necessary, a properly applied and secured marking tape from the road pavement, for example when the location of the marking is to be modified.